Dimerization of Oxaallyl, Azaallyl, Oxaphosphaallyl, and Oxathiaallyl Groups by Way of Organocopper Compounds

Scope and Mechanism of Direct Indole and Pyrrole Couplings Adjacent to Carbonyl Compounds: Total Synthesis of Acremoauxin A and Oxazinin 3

“…In 1968, Kauffmann reported the first example of an oxidative dimerization of a ketone enolate, namely acetophenone, using copper(I) salts, albiet in modest yields. 19 29,33 which show the versatility of this coupling reaction in the formation of a wide variety of dimerized compounds. Several reports exist that elicit the coupling of other stabilized anions, such as phosphine oxides, 34 sulfoxides/sulfones, 34 and methylpyridines 36b under similar conditions.…”

“…During these intervening years, little was truly known about the reaction or substrate scope; in fact, to this day, many questions remain unanswered concerning this intriguing reaction. In 1968, Kauffmann reported the first example of an oxidative dimerization of a ketone enolate, namely acetophenone, using copper(I) salts, albiet in modest yields . Following this publication, Rathke reported the first use of a soluble copper(II) oxidant [copper(II) valerate] in the oxidative dimerization of ester enolates in moderate to excellent yields …”

“…He also described the heterocoupling of two different ketone enolates, which required 3 equiv or more of one of the coupling partners to furnish acceptable yields of the heterocoupled product. Many reports have appeared that use a wide variety of oxidants to effect the couplings, including copper salts, 18b,c,− ,23c,d,24m,,26d iron salts, 18d,,37d,e iodine, 18a,c,23d,,28b,,37a-c N -iodosuccinimide, hypervalent iodine-based reagents, silver salts, 18b, titanium salts, 26d, potassium permanganate, direct electrochemical oxidation, 18a, short chain alkyl polyhalides, and bromine. , A few studies involving the dimerization of enolates conjugated throughout an aromatic system have been reported, , which show the versatility of this coupling reaction in the formation of a wide variety of dimerized compounds. Several reports exist that elicit the coupling of other stabilized anions, such as phosphine oxides, sulfoxides/sulfones, and methylpyridines 36b undersimilar conditions.…”

“…In 1968, Kauffmann reported the first example of an oxidative dimerization of a ketone enolate, namely acetophenone, using copper(I) salts, albiet in modest yields. 19 Following this publication, Rathke reported the first use of a soluble copper(II) oxidant [copper(II) valerate] in the oxidative dimerization of ester enolates in moderate to excellent yields. 20 Saegusa subsequently demonstrated efficient, high-yielding dimerizations of ketone enolates, using a variety of copper(II) based oxidants.…”

Anticancer Molecule Discovery via C2-Substituent Promoted Oxidative Coupling of Indole and Enolate

“…Among many excellent coupling strategies, we would like to develop oxidative coupling of C2-substituted indoles and enolates without carbon-metal bond formation, given that aryl halide could not be well tolerated in many transition-metals-catalyzed reactions (Sun et al., 2010, Wendlandt et al., 2011, Liu et al., 2011, Yeung and Dong, 2011, Zhang et al., 2012), which will restrict the derivatization of products to certain extent. Oxidative homocoupling of enolates was discovered in 1935, but limited progress was achieved in the following 50 years (Babler and Haack, 1983, Brocksom et al, 1975, Guo et al., 2012, Ito et al., 1975, Ito et al., 1977, Ivanoff and Spasoff, 1935, Kauffmann et al., 1968, Ojima et al., 1992, Rathke and Lindert, 1971). Baran first reported the intermolecular cross-coupling of indoles and enolates under similar reaction conditions via a copper-chelated radical-anion coupling procedure (Baran and Richter, 2004).…”